10(l) Crustal Deformation Processes: Folding and Faulting CHAPTER 10: Introduction to the Lithosphere (l). Crustal Deformation Processes: Folding and Faulting The topographic map illustrated in Figure 10l-1 suggests that the Earth's surface has been deformed. This deformation is the result of forces that are strong enough to move ocean sediments to an eleveation many thousands meters above sea level. In previous lectures, we have discovered that this displacement of rock can be caused by tectonic plate movement and subduction , volcanic activity , and intrusive igneous activity . Figure 10l-1: Topographic relief of the Earth's terrestrial surface and ocean basins. Ocean trenches and the ocean floor have the lowest elevations on the image and are colored dark blue. Elevation is indicated by color. The legend below shows the relationship between color and elevation. (Source: National Geophysical Data Center , National Oceanic and Atmospheric Administration). Deformation of rock involves changes in the shape and/or volume of these substances. Changes in shape and volume occur when stress and strain causes rock to buckle and fracture or crumple into folds.

A fold can be defined as a bend in rock that is the response to compressional forces. Folds are most visible in rocks that contain layering. For plastic deformation of rock to occur a number of conditions must be met, including: The rock material must have the ability to deform under pressure and heat. The higher the temperature of the rock the more plastic it becomes. Pressure must not exceed the internal strength of the rock. If it does, fracturing occurs. Deformation must be applied slowly. A number of different folds have been recognized and classified by geologists. The simplest type of fold is called a monocline (Figure 10i-2). This fold involves a slight bend in otherwise parallel layers of rock. Figure 10l-2: Monocline fold. An anticline is a convex up fold in rock that resembles an arch like structure with the rock beds (or limbs) dipping way from the center of the structure (Figure 10l-3). Figure 10l-3: Anticline fold. Note how the rock layers dip away from the center of the fold are roughly symmetrical.

A syncline is a fold where the rock layers are warped downward (Figure 10l-4 and 10l-5). Both anticlines and synclines are the result of compressional stress. Figure 10l-4: Syncline fold. Note how the rock layers dip toward the center of the fold and are roughly symmetrical. Figure 10l-5: Synclinal folds in bedrock, near Saint-Godard-de-Lejeune, Canada. (Source: Natural Resources Canada - Terrain Sciences Division - Canadian Landscapes ). More complex fold types can develop in situations where lateral pressures become greater. The greater pressure results in anticlines and synclines that are inclined and asymmetrical (Figure 10l-6). Figure 10l-6: The following illustration shows two anticline folds which are inclined. Also note how the beds on either side of the fold center are asymmetrical. A recumbent fold develops if the center of the fold moves from being once vertical to a horizontal position (Figure 10l-7). Recumbent folds are commonly found in the core of mountain ranges and indicate that compression and/or shear forces were stronger in one direction.

Extreme stress and pressure can sometimes cause the rocks to shear along a plane of weakness creating a fault . We call the combination of a fault and a fold in a rock an overthrust fault . Figure 10l-7: Recumbent fold. Faults form in rocks when the stresses overcome the internal strength of the rock resulting in a fracture. A fault can be defined as the displacement of once connected blocks of rock along a fault plane. This can occur in any direction with the blocks moving away from each other. Faults occur from both tensional and compressional forces. Figure 10l-8 shows the location of some of the major faults located on the Earth. Figure 10l-8: Location of some of the major faults on the Earth. Note that many of these faults are in mountainous regions (see section 10k ). There are several different kinds of faults. These faults are named according to the type of stress that acts on the rock and by the nature of the movement of the rock blocks either side of the fault plane. Normal faults occur when tensional forces act in opposite directions and cause one slab of the rock to be displaced up and the other slab down (Figure 10l-9).

Figure 10l-9: Animation of a normal fault. Reverse faults develop when compressional forces exist (Figure 10l-10). Compression causes one block to be pushed up and over the other block. Figure 10l-10: Animation of a reverse fault. A graben fault is produced when tensional stresses result in the subsidence of a block of rock. On a large scale these features are known as Rift Valleys (Figure 10l-11). Figure 10l-11: Animation of a graben fault. A horst fault is the development of two reverse faults causing a block of rock to be pushed up (Figure 10l-12). Figure 10l-12: Animation of a horst fault. The final major type of fault is the strike-slip or transform fault . These faults are vertical in nature and are produced where the stresses are exerted parallel to each other (Figure 10l-13). A well-known example of this type of fault is the San Andreas fault in California. Figure 10l-13: Transcurrent fault zones on and off the West coast of North America. (Source: U.S.

Geological Survey). GEY 101 - Introductory Geology: Exploring Planet Earth GEY 101 - Introductory Geology: Exploring Planet Earth Deformation Structural geologists study the architecture and processes responsible for deformation of Earth�s crust A working knowledge of rock structures is essential to our modern way of life Deformation is a general term that refers to all changes in the original form and/or size of a rock body Most crustal deformation occurs along plate margins Deformation involves: Force - that which tends to put stationary objects in motion or changes the motions of moving objects Concepts stress - causes strain (deformation), the force applied to a volume of rock. strain - change in shape caused by stress, the deformation caused by stress, strain can take place by folding or faulting. Types of stress tension <---- -----> : Tension is the stretching of rocks. compression -----> <------ : Compression is the squeezing together of rocks. shear stress is pulling in opposite directions to provide a rolling stress.

Strain Elastic deformation - the rock returns to nearly its original size and shape when the stress is removed Once the elastic limit (strength) of a rock is surpassed, it either flows (ductile deformation) or fractures (brittle deformation) types brittle - fracture, break; If rocks are deformed quickly or are hard, they will Fracture ductile - bend, fold (plastic deformation); Plastic Deformation when rocks are soft enough of are stressed slowly enough they will deform plastically and flow. controlling factors time rock type Mapping geologic structures When conducting a study of a region, a geologist identifies and describes the dominant rock structures Usually only a limited number of outcrops (sites where bedrock is exposed at the surface) are available Work is aided by advances in aerial photography, satellite imagery and Global Positioning Systems (GPS) Describing and mapping the orientation or attitude of a rock layer or fault surface involves determining the features; Strike and Dip tell us the orientation of rocks.

Strike (trend) The compass direction of the line produced by the intersection of an inclined rock layer or fault with a horizontal plane Generally expressed an an angle relative to north Dip (inclination) The angle of inclination of the surface of a rock unit or fault measured from a horizontal plane Includes both an of inclination and a direction toward which the rock is inclined Ductile Deformation -- Folds During crustal deformation rocks are often bent into a series of wave-like undulations called folds Characteristics of folds Limbs - refers to the two sides of a fold Axis - a line drawn down the points of maximum curvature of each layer Axial plane - an imaginary surface that divides a fold symmetrically Ductile deformation -- folds Anticline - upfolded or arched rock layers Syncline - downfolds or troughs of rock layers Depending on their orientation, anticlines and synclines can be described as Symmetrical, asymmetrical, recumbent (an overturned fold), or plunging Asymmetrical folds are when one side is steeper than the other. Overturned folds are where one side is tipped underneath. Plunging folds. are where one end of the fold is diving into the ground.

Monoclines - large, step-like folds in otherwise horizontal sedimentary strata; Monoclines are often the result of movement along buried faults Dome Deformation of Rock Mountain Building Processes Stress and Strain We start our discussion with a brief review of the concepts of stress and strain. Recall that stress is a force acting on a material that produces a strain. Stress is a force applied over an area and therefore has units of Force/area (like lb/in 2 ). Pressure is a stress where the forces act equally from all directions. If stress is not equal from all directions then we say that the stress is a differential stress. Three kinds of differential stress occur. Tensional stress (or extensional stress), which stretches rock; Compressional stress, which squeezes rock; and Shear stress, which result in slippage and translation. When rocks deform they are said to strain. A strain is a change in size, shape, or volume of a material. We here modify that definition somewhat to say that a strain also includes any kind of movement of the material, including translation and tilting. Stages of Deformation Fracture - irreversible strain wherein the material breaks.

We can divide materials into two classes that depend on their relative behavior under stress. Brittle materials have a small or large region of elastic behavior but only a small region of ductile behavior before they fracture. Ductile materials have a small region of elastic behavior and a large region of ductile behavior before they fracture. How a material behaves will depend on several factors. Among them are: Temperature - At high temperature molecules and their bonds can stretch and move, thus materials will behave in more ductile manner. At low Temperature, materials are brittle. Confining Pressure - At high confining pressure materials are less likely to fracture because the pressure of the surroundings tends to hinder the formation of fractures. At low confining stress, material will be brittle and tend to fracture sooner. Strain rate -- At high strain rates material tends to fracture. At low strain rates more time is available for individual atoms to move and therefore ductile behavior is favored. Composition -- Some minerals, like quartz, olivine, and feldspars are very brittle. Others, like clay minerals, micas, and calcite are more ductile This is due to the chemical bond types that hold them together.

Thus, the mineralogical composition of the rock will be a factor in determining the deformational behavior of the rock. Another aspect is presence or absence of water. Water appears to weaken the chemical bonds and forms films around mineral grains along which slippage can take place. Thus wet rock tends to behave in ductile manner, while dry rocks tend to behave in brittle manner. Brittle-Ductile Properties of the Lithosphere We all know that rocks near the surface of the Earth behave in a brittle manner. Crustal rocks are composed of minerals like quartz and feldspar which have high strength, particularly at low pressure and temperature. As we go deeper in the Earth the strength of these rocks initially increases. At a depth of about 15 km we reach a point called the brittle-ductile transition zone. Below this point rock strength decreases because fractures become closed and the temperature is higher, making the rocks behave in a ductile manner. At the base of the crust the rock type changes to peridotite which is rich in olivine. Olivine is stronger than the minerals that make up most crustal rocks, so the upper part of the mantle is again strong.

But, just as in the crust, increasing temperature eventually predominates and at a depth of about 40 km the brittle-ductile transition zone in the mantle occurs. Below this point rocks behave in an increasingly ductile manner. Deformation in Progress Only in a few cases does deformation of rocks occur at a rate that is observable on human time scales. Abrupt deformation along faults, usually associated with earthquakes occurs on a time scale of minutes or seconds. Gradual deformation along faults or in areas of uplift or subsidence can be measured over periods of months to years with sensitive measuring instruments. Evidence of Past Deformation Evidence of deformation that has occurred in the past is very evident in crustal rocks. For example, sedimentary strata and lava flows generally follow the law of original horizontality. Thus, when we see such strata inclined instead of horizontal, evidence of an episode of deformation. Since many geologic features are planar in nature, we a way to uniquely define the orientation of a planar feature we first need to define two terms - strike and dip. For an inclined plane the strike is the compass direction of any horizontal line on the plane.

The dip is the angle between a horizontal plane and the inclined plane, measured perpendicular to the direction of strike. In recording strike and dip measurements on a geologic map, a symbol is used that has a long line oriented parallel to the compass direction of the strike. A short tick mark is placed in the center of the line on the side to which the inclined plane dips, and the angle of dip is recorded next to the strike and dip symbol as shown above. For beds with a 900 dip (vertical) the short line crosses the strike line, and for beds with no dip (horizontal) a circle with a cross inside is used as shown below. For linear structures, a similar method is used, the strike or bearing is the compass direction and angle the line makes with a horizontal surface is called the plunge angle. Fracture of Brittle Rocks As we have discussed previously, brittle rocks tend to fracture when placed under a high enough stress. Such fracturing, while it does produce irregular cracks in the rock, sometimes produces planar features that provide evidence of the stresses acting at the time of formation of the cracks. Two major types of more or less planar fractures can occur: joints and faults.

Joints As we learned in our discussion of physical weathering, joints are fractures in rock that show no slippage or offset along the fracture. Joints are usually planar features, so their orientation can be described as a strike and dip. They form from as a result of extensional stress acting on brittle rock. Such stresses can be induced by cooling of rock (volume decreases as temperature decreases) or by relief of pressure as rock is eroded above thus removing weight. Joints provide pathways for water and thus pathways for chemical weathering attack on rocks. If new minerals are precipitated from water flowing in the joints, this will form a vein. Many veins observed in rock are mostly either quartz or calcite, but can contain rare minerals like gold and silver. These aspects will be discussed in more detail when we talk about valuable minerals from the earth in a couple of weeks. Because joints provide access of water to rock, rates of weathering and/or erosion are usually higher along joints and this can lead to differential erosion. From an engineering point of view, joints are important structures to understand. Since they are zones of weakness, their presence is critical when building anything from dams to highways. For dams, the water could leak out through the joints leading to dam failure.

For highways the joints may separate and cause rock falls and landslides. Faults Faults occur when brittle rocks fracture and there is an offset along the fracture. When the offset is small, the displacement can be easily measured, but sometimes the displacement is so large that it is difficult to measure. Types of Faults As we found out in our discussion of earthquakes, faults can be divided into several different types depending on the direction of relative displacement. Since faults are planar features, the concept of strike and dip also applies, and thus the strike and dip of a fault plane can be measured. One division of faults is between dip-slip faults, where the displacement is measured along the dip direction of the fault, and strike-slip faults where the displacement is horizontal, parallel to the strike of the fault. Recall the following types of faults: Dip Slip Faults - Dip slip faults are faults that have an inclined fault plane and along which the relative displacement or offset has occurred along the dip direction. Note that in looking at the displacement on any fault we don't know which side actually moved or if both sides moved, all we can determine is the relative sense of motion.

Normal Faults - are faults that result from horizontal tensional stresses in brittle rocks and where the hanging-wall block has moved down relative to the footwall block. Horsts & Grabens - Due to the tensional stress responsible for normal faults, they often occur in a series, with adjacent faults dipping in opposite directions. In such a case the down-dropped blocks form grabens and the uplifted blocks form horsts. In areas where tensional stress has recently affected the crust, the grabens may form rift valleys and the uplifted horst blocks may form linear mountain ranges. The East African Rift Valley is an example of an area where continental extension has created such a rift. The basin and range province of the western U.S. (Nevada, Utah, and Idaho) is also an area that has recently undergone crustal extension. In the basin and range, the basins are elongated grabens that now form valleys, and the ranges are uplifted horst blocks. Half-Grabens - A normal fault that has a curved fault plane with the dip decreasing with depth can cause the down-dropped block to rotate.

In such a case a half-graben is produced, called such because it is bounded by only one fault instead of the two that form a normal graben. Reverse Faults - are faults that result from horizontal compressional stresses in brittle rocks, where the hanging-wall block has moved up relative the footwall block. A Thrust Fault is a special case of a reverse fault where the dip of the fault is less than 45o. Thrust faults can have considerable displacement, measuring hundreds of kilometers, and can result in older strata overlying younger strata. Strike Slip Faults - are faults where the relative motion on the fault has taken place along a horizontal direction. Such faults result from shear stresses acting in the crust. Strike slip faults can be of two varieties, depending on the sense of displacement. To an observer standing on one side of the fault and looking across the fault, if the block on the other side has moved to the left, we say that the fault is a left-lateral strike-slip fault. If the block on the other side has moved to the right, we say that the fault is a right-lateral strike-slip fault. The famous San Andreas Fault in California is an example of a right-lateral strike-slip fault.

Displacements on the San Andreas fault are estimated at over 600 km. Evidence of Movement on Faults Since movement on a fault involves rocks sliding past each other there may be left evidence of movement in the area of the fault plane. Fault Breccias are crumbled up rocks consisting of angular fragments that were formed as a result of grinding and crushing movement along a fault. When the rock is broken into clay or silt size particles as a result of slippage on the fault, it is referred to as fault gouge. Slickensides are scratch marks that are left on the fault plane as one block moves relative to the other. Slickensides can be used to determine the direction and sense of motion on a fault. Mylonite - Along some faults rocks are sheared or drawn out by ductile deformation along the fault. This results in a type of localized metamorphism called dynamic metamorphism (also called cataclastic metamorphism. The resulting rock is a fine grained metamorphic rock show evidence of shear, called a mylonite. Faults that show such ductile shear are referred to as shear zones.

Deformation of Ductile Rocks When rocks deform in a ductile manner, instead of fracturing to form faults or joints, they may bend or fold, and the resulting structures are called folds. Folds result from compressional stresses or shear stresses acting over considerable time. Because the strain rate is low and/or the temperature is high, rocks that we normally consider brittle can behave in a ductile manner resulting in such folds. Geometry of Folds - Folds are described by their form and orientation. The sides of a fold are called limbs. The limbs intersect at the tightest part of the fold, called the hinge. A line connecting all points on the hinge is called the fold axis. An imaginary plane that includes the fold axis and divides the fold as symmetrically as possible is called the axial plane of the fold. We recognize several different kinds of folds. Monoclines are the simplest types of folds. Monoclines occur when horizontal strata are bent upward so that the two limbs of the fold are still horizontal. Anticlines are folds where the originally horizontal strata has been folded upward, and the two limbs of the fold dip away from the hinge of the fold.

Synclines are folds where the originally horizontal strata have been folded downward, and the two limbs of the fold dip inward toward the hinge of the fold. Synclines and anticlines usually occur together such that the limb of a syncline is also the limb of an anticline. Exam 3 - Geology 1403 with Dalman at Blinn College - StudyBlue the freefall of all detatched pieces Talus slopes are built by... Rockfalls There is a distinct zone of weakness separating the slide material from the underlying material Rotational Slide surface of rupture is concave up Transitional slide material moves along a flat surface Flow material moves downslope in a viscous fluid Rock Avalanche Most rapid type of mass wasting Rocks float on air as they move downslope Creep Particles move a few millimeters per year Slump the movement of a mass of rock or unconsolidated material as a unit along a curved surface occurs along oversteepened slopes Occurs when blocks of bedrock slide down a slope Generally very fast and destructive Sometime triggered by earthquakes sometimes triggered by melting snow or rain When are rockslides most common?

During the spring rapid form of mass wasting that involves the flow of soil and regolith with water Fine grained debris flow debris flows are confined to... channels and canyons What causes debris flow in semiarid regions? sudden rainfall or snow melt washes large quantities of sediment into rivers Lack of vegetation to anchor soil Lahar Debris flows composed mostly of volcanic material An example of lahar is... Mt. St. Helens on hillsides in humid regions during heavy percipitation or snowmelt Earthflows commonly involve materials rich in... clay and silt the alternate expansion and attraction of the surface material What causes fences and utility walls to tilt? Creep The downslope movement of water logged soils Solifluction is promoted by... a dense clay hardpan or impermeable bedrock layer Solifluction is common in regions underlain by... permafrost Movement of material under the influence of gravity alone How is a fall different from creep? Falls occur rapidly and in areas with high slope, whereas creep occurs slowly in areas with low slope. How are slumps and slides related? Slumps are a type of slide in the special case where the rupture surface is curved. How are debris avalanches and flows related?

Debris avalanches are large, rapid flows of rock. A __________ is formed when vertical incision by a stream is the primary process, with relatively minimal mass wasting. Slot Canyon Which of the following correctly states the role of rivers and mass wasting in the formation of the Grand Canyon? The Colorado River erodes downward, then mass-wasting processes move material from high to low areas, then the Colorado River transports material downstream. Over time, mass wasting causes __________. Canyons to widen What rock type is the easiest for a river to cut through? Shale When considering mass wasting, which of the following factors is most influential in the downslope movement of weathered particles? Gravity When dry sediment accumulates, the angle of repose represents what property of the deposit? The steepest angle at which those sediments can accumulate and remain stable When sediment accumulates, the angle of repose can be increased by changing which of the following conditions? slight addition of water to the sediment Describe how a soil particle moves downhill during the freeze thaw process During the freeze, a soil particle moves at a right angle away from the surface, and thawing causes the particle to fall back to a slightly lower level.

__________ is an example of mass wasting commonly seen in the active layer above permafrost Solifluction What is name of the near-surface layer that thaws in the summer? The active layer f permafrost is melted, which of the following is a consequence? The ground subsides because the volume of water is less than that of ice. Which of the following was a major factor leading to the Gros Ventre, WY, slide? Soils and shallow bedrock were very wet and locally saturated. Which of the following materials has the maximum sustainable slope angle as determined by the angle of repose? Dry Sand What can happen to the downhill toe of a slump during wet weather or times when snow is melting? The toe can become an earthflow A geologist wants to locate a horizontal coal bed on a soil-covered slope where soil creep is active. A distinctive sandstone bed underlies the coal bed. On the basis of weathered sandstone fragments in the soil, where is the coal bed? Just above the highest sandstone seen in the soil Consider a steep highway cut made by removing granite bedrock with conditions ranging from slightly weathered to fresh and fractured. Which of the following situations is the most stable against rockslides?

One set of widely spaced subhorizontal fractures Which of the following mass wasting processes involves movement of rock on a zone of compressed air? Rock avalanche How do freezing, thawing, wetting, and drying contribute to soil creep? The soil expands and contracts, lifting particles and dropping them a slight distance downslope Which of the following disasters was triggered by a huge mass of soil and rock that suddenly slid into a water-filled reservoir? Vaiont Canyon, Italy, 1963 Which of the following terms denotes the exposed, crescent-shaped rupture surface at the head of a slump? Scarp Which of the following mass movements is most likely to occur in a geologic setting where the rock strata are inclined? Rockslide What caused the 1985 mudflows on the Nevado del Ruiz volcano? Hot ash fell onto the snow near the summit Hydrologic cycle describes the movement of water through earths four spheres How much of the earth is salt water? 96.5% anytime water flows in a channel, regardless of size River carries a substantial amount of water and has many tributaries Rivers drain much of the land area except for in...

extremely arid or polar regions {} and {} influence the character of a river climate differences and human intervention laminar flow water slowly flowing in a nearly straight path turbulent flow water moving quickly in an arratic fashion (both horizontal and vertical) gradient slop of stream - the steeper the gradient the faster the flow wetted perimiter how much area is in contact with waater - the more contact the more friction Discharge the volume of water flowing past a certain point in a given unit of time Longitudinal profile a cross-sectional view of a stream most longitudinal profiles have {} shape concae a {} stream only transports sediments graded meanders flowing through steep, narrow bedrock valleys terraces the flat remnants of the old flood plain Deltas form when sediment filled streams enter a large bed of water distributaries the main channel divides into several smaller channels in the delta natural levees raised areas adjacent to the channel formed during flood events alluvial fans fan-shaped deposits of sediments at the base of mountain fronts A flood occurs when...

the stream exceeds capacity of its channel Regional floods seasonal floods that typically result from spring rains or rapid melting of snow flash flood occur with little to no warning in mountaneous areas Ice jam floods ice forms in rivers creating dams that will break when temperatures rise Artificial levees earth mounds built on riverbanks to increase the capacity of the channel - often fail in floods Chanelization altering a stream channel to make flow more efficient - increases erosion Non structural approach to flood control best approach to flood control is to limit development within the flood plain How can pieces of rock in contact with a stream bed move? Rolling, Slinding, Suspension Complete this analogy: Bouncing is to sand as suspension is to_____________. Clay Complete this analogy: Sliding is to gravel as dissolution is to_____________ Ions What is part of the bed load? Gravel and Sand What are the three types of loads carried by streams? Bed load, suspended load, dissolved load Suspended Load the fine-grained particles that travel in the water column above the stream bed What type of stream is associated with the formation of an oxbow lake? meandering stream What is the dominant fluvial process in a clear, sediment-poor stream moving down a steep slope?

downcutting Which processes result in the widening of the floodplain of a meandering stream? Undercutting and lateral erosion Where do deposition and erosion of material occur along a meander? Deposition occurs on the inside of the meander, whereas erosion occurs on the outside What is an oxbow lake? a meander that has been cut off from the original stream channel How are oxboe lakes formed? Oxbow lakes form when one meander erodes into another, cutting off water to part of the stream channel. Meander Scar landscape feature formed after an oxbow lake dries up What causes meandering streams to downcut and become incised meanders? uplift of land the stream is flowing on Which of the following is likely to occur to an incised meander after it reaches equilibrium with its new base level? the incised meander will cause only minor erosion to the canyon walls Incising meanders erode primarily by... downcutting Meanders in equilibrium erode... in a side to side manner Which of the following features would you expect to find on the outside bank of a stream meander loop?

A cutbank When the local gradient of a stream changes as it goes from a mountainous area to a large flat-lying area, which of the following features could form? an alluvian fan Stream terraces form as the result of which of the following processes? Downcutting following the rise of the landscape produces stream terraces. While working in the field, you come upon a stream that flows in a very deep V-shaped valley. Regarding the history of this stream, which of the following statements is most likely true? the stream is raltively young In a delta, sedimentary layers deposited under circumstances that appear to violate the Principle of Original Horizontality are found in which of the following circumstances? foreset beds Water falling in Illinois would ultimately end up where? gulf of mexico Which of the following is the primary step that allows water to enter the groundwater system? Infiltration hich of the following statements about the global water supply is true? decreased percipitation to impact water supply available for humans Flood plain flat surface next to a river channel Natural levee ridge of flood deposits next to a river channel How does the formation of a natural levee impact flooding?

Natural levees raise the height of the stream channel, reducing the amount of flooding that will occur on the floodplain. How does urbanization (paving, etc.) affect runoff and infiltration in a small, previously forested drainage basin? Infiltration decreases, runoff increases What term describes the particle transport mode that is intermediate between suspension and rolling along the bottom of streams? This process also moves sand grains in a sand dune. Saltation Which of the following was the cause of the extraordinarily severe flooding on the Mississippi River and its tributaries in 1993? The upper basin of the Mississippi sustained very heavy rainfall in the late spring and early summer. A dam and a reservoir are constructed on a graded river. What will happen? Deposition upstream from the dam; channel downcutting below Which one of the following rivers has the largest water discharge of any in the world? Amazon What term generally refers to the highest percentage of the annual sediment load moved by a stream? Suspended load Which of the following must result in a lower base level for rivers and streams? Sea level falls or land rises Which of the following features characterize wide streams and valleys?

natural levees and broad flood plains Many large rivers in the Colorado Plateau region meander in deep, narrow canyons and have no floodplains. How could this have happened? Original old-age streams downcut as the land gradually rose. What is the term for the drop in water surface elevation divided by the distance the water flows? stream gradient Which one of the following best describes how urbanization affects small-stream watersheds? Infiltration decreases; lag time between storms and peak runoff shortens. Sea level {} when water is stored in expanding ice sheets and continental glaciers. drops What type of stream pattern develops only on growing mountains like volcanoes or where the land surface is tectonically doming upward? Radial Which of the following was the cause of the extraordinarily severe flooding on the Mississippi River and its tributaries in 1993? the upper basin sustained very heavy rainfall Which of the following pairs of words are components of the hydrologic cycle that release water vapor directly into the atmosphere? evaporation and transportation What type of drainage pattern generally develops in areas underlain by tilted or folded strata, where tributary streams flow along outcrop areas of soft strata?

trellis In the __________, groundwater fills the pore space. zone of saturation the {} surface is a subdued version of the surface topography water table A __________ is separated from the groundwater system by the unsaturated zone. losing stream (disconnected) How would the water table be affected if Earth were made up of uniform, permeable material? the water table would not exist why does groundwater discharge to earth's surface Earth's surface is irregular, and permeability decreases with depth within Earth. Which of the following would produce a LOWER water table? increase in discharge, decrease in recharge how does the use of water by humans affect the water talble? Use of water by humans increases discharge, resulting in lowered water tables. How does the water table change around a pumping water well? the water table elevation decreases what is the cone of depression? the shape that the water table takes on near a pumping well when will a cone of depression stop enlarging? when the amount of water flowing toward the well equals the amount of water being pumped out of the well when might a well, wellA, go dry? when the cone of depression of a second well intersects the deepest part of Well A A(n) __________ acts as a conduit that brings heated water to the surface.

fault What prevents water at the bottom of the underground caverns from boiling at the normal surface temperature? The pressure from the weight of overlying water causes the boiling point to increase Once overlying water heats to a sufficient temperature, it __________ and releases pressure on the water below flashes to steam Which common, rock-forming mineral or mineral group is most readily dissolved by groundwater? calcite An artesian system is present when groundwater __________ under pressure rises above the aquifer level A __________ is located where the pressure surface is above the aquifer, but below the ground a non flowing artesian well If a well is drilled into an aquifer where the pressure surface is both above the aquifer and the ground, a __________ is formed. a flowing artesian well Which of the following is a requirement for an artesian system to exist?

an aquitard must be present both above and below the aquifer As shown by the South Dakota example, artesian systems __________ are able to transmit water great distances from recharge to discharge areas groundwater water found in the pores of soil and sediment, plus narrow fractures in bedrock {} is the largest resevoir of freshwater groundwater Zone of soil moisture a zone where water is held by a molecular attraction on soil particles in the near-surface zone Zone of saturation zone where all of the pore spaces are completely filled with water water table the upper limit of the zone of saturation the unsaturated zone includes a {}, a region where groundwater is held in pore spaces by surface tenssion capillary fringe where is the unsaturated zone located? above the zone of saturation gaining stream gain water from the inflow of groundwater through the stream bed - water table is higher than stream surface losing stream lose water to the groundwater system by outflow through the stream bed - water table is lower than stream surface Can a stream be both gaining and losing? yes the percent of pore (open) spaces in a rock or sediment Poorly sorted sediments have a {} porosity low how much groundwater can be stored Permeability the ability of material to transmit a fluid Permeability depends on...

an impermeable layer that hinders or prevents water movement - ex: clay aquifer permeable rock strata or sediment that transmit groundwater freely - Ex: sands and gravel Groundwater moves at an average rate of ... 4 cm per day A simple groundwater flow system is... the force of gravity adn pressure differences move groundwater Groundwater is replinished in areas of {} recharge Groundwater flows back to the surface in areas of {} discharge Darcy's Law a measure of the volume of water that flows through an aquifer, using the hydraulic gradient, conductivity and cross sectionalarea Hydraulic gradient the water table slope {} takes into account the permeability of the aquifer adn viscousity of the liquid to determin how fast waater will flow through a medium hydraulic conductivity hole bored into the zone of saturation What is the most common method of removing groundwater? well as water is withdrawn from the wall, the surrounding water table is lowered a {} forms around a well cone of depression an artisian well or spring is a system where... groundwater under pressure rises above the level of the aquifer confined aquifer in a non flowing artisian well pressure surface is {} ground level below in a flowing artisian well pressure surface is {} ground level above Springs occur where...

the water table interseccts earth's surface - natural outflow of groundwater springs can be caused by an aquitard creating a localized zone of saturation which is called... a perched water table the water for most hot springs is heated by... the cooling of igneous rocks - some is heated by the geothermal gradient Geysers intermittent hot springs in which columns of water errupt with force Where do geysers occur? where extensive under ground chambers exist within hot igneous rock How do geysers work? groundwater heats, expands, changes to steam and errupts subsidence the groundwater sinks when water is pumped from wells faster than natural recharge process can replace it What is a common source of groundwater contamination? sewage a sinking well can lead to... groundwater pollution acidic groundwater dissolving soluable rock Speleothem general name for all dripstone features Karst topography a landscape that has been shaped mainly by the dissolving power of groundwater Sinkshades formed by groundwater slowly dissolving the bedrock often accompanied by collapse Which of the following statements defines the aerated, or vadose, zone? the aerated or vadose zone lies above the water table when will a perched water table develop?

When a horizontal aquitard above the regional water table lies below an aquifer Which of the following are specific features of karst topography? treams flow into depressions called sinkholes and continue to flow underground. which best describes how geysers errupt? With a slight reduction in pressure, water in a saturated, natural conduit suddenly boils, sending a plume of steam and hot water into the air above the vent. The hot spring deposits at Mammoth Hot Springs, Yellowstone National Park, are travertine. What rock probably lies somewhere beneath the hot springs? limestone How would hazardous substances such as gasoline, kerosene, ethyl alcohol, pesticides, and acids that accidentally entered a groundwater system behave? Gasoline and kerosene would float on the water table; ethyl alcohol would dissolve and disperse in the groundwater. What is the relationship between drawdown and the cone of depression associated with a pumping well? drawdown is the distance between the original water table and the water in the well Which of the following statements concerning unconfined aquifers on barrier islands and atolls is correct? Any salt water in the aquifer will rise if the water table is lowered by pumping What force pushes groundwater from pore to pore below the water table?

pressure gradient or hyraulic gradient what is an unconfined water table? The boundary between the aerated, or vadose, zone above and the saturated zone below Which of the following describes a disappearing (sinking) creek? an influent stream in a karst area Which of the following materials would have the best capability to naturally remove sewage pollutants? slightly clayey sand Deformation a general term that refers to changes in the shape or position of a rock body in response to stress {} are the features that result from forces generated by the interactions of tectonic plates rock or geological structres the force that deforms rocks Stress applied uniformally in all directions is... confining pressure stress applied unequally in different directions is...

differential stress {} stress squeezes a rock and shortens a rock body compressional {} stress pulls apart a rock unit and lengthens it tensional {} stress produces a motion similar to slippage shear the change in shape caused by stress Elastic deformation the rock returns to nearly its original size and shape when the rock is removed Once elastic limit of a rock is surpassed it either {} or {} bends (ductile deformation) or breaks (brittle deformation) Higher temperature rocks deform by {} deformation ductile cooler temperature rocks deform by {} deformation brittle What does confining pressure do to rocks?

squeezesthem, making them stronger and harder to break crystalline igneous rocks generally experience {} deformation brittle sedimentary and metamorphic rocks generally experience {} deformation ductile forces applied over a long period of time generally result in {} deformation ductile upfolded or arched sedimentary layers - oldest strata are in the middle synclines downfolded or troughs of rock layers - yougest strata are in the center Domes upward circular features - oldest rocks in center Basins downward circular feature - youngest rocks in center monoclines large, step like folds in otherwise horizontal sedimentary strata faults fractures in rocks, along which displaacaement has occured WHat makes a joint different from a fault? theres no movement {} faults occur when movement is parallel to the incline dip-slip rock surface above the fault footwall rock surface below the fault the vertical displacement along the fault produces long, low cliffs called {} fault scarps {} faults are characterized by the hanging wall moving down relative to the footwall normal Larger scaale normal faults are associated with...

fault block mountains the boundary between ductile and brittle rock units {} faults are characterized by the hanging wall moving up relative to the foot walal reverse {} faults have an angle less than 45 degrees so the overlying plate moves almost horizontally thrust {} faults are characterized by placement that is horizontal and parallel to the stike of the fault strike-slip large strike slip faults that cut through crust to accomodate plate motion are call... transform faults the process that collectively produces a mountain belt suture zone where two continents collide most compressional mountains exhibit the deformation of a thick sequence of sedimentary rocks called a... fold and thrust belt the concept of floating crust in gravitational balance gravitational collapse the ductile spreading adn consequential subduction Which of the following scenarios could result in the development of a compressional mountain belt? two land masses collide Which geologic features would be present in compressional mountain belts? folds, intrusive igneous rocks, thrust faults Which of the following rocks are characteristic of compressional mountain building? schist Which type of force causes folding? compressional force a fold shaped like an upside down u What is a syncline? a fold shaped like a right side up U Imagine an anticline has been eroded to a flat surface.

How would the rock age change as you walked across that flat surface? rock would be youngest on the edges and oldest in the middle Imagine a syncline has been eroded to a flat surface. How would the rock age change as you walked across that flat surface? rock would be oldest on the edges and youngest in the middle What produces plunging folds? a combination of folding and tilting What does the term plunging fold mean? a fold that is tilted down into earth Imagine a fold has been eroded to a flat surface. In general, how would you know whether this fold is plunging? non plunging folds look like straight lines at the surface adn plunging folds look wavy Which of the following statements best describes the orientation of rock layers for a structural dome or structural basin? rock layers wrap around a single point If strike and dips symbols were placed on a map of a basin, which way would the dips point? dips point down toward the center Which fault will see the hanging wall move down relative to the footwall? normal fault __________ faults combine elements of strike-slip and dip-slip motions. oblique slip What is the geologic term for folded rocks with the bend at the bottom?

syncline mats of blue-green algae that grew in mounds up from the sea floor What does a turbidite sequence consist of? a blanket of sand overlain by a sheet of mud What caused metamorphism to occur in the Blue Ridge District during the Alleghanian Orogeny? strong differential stress When did Pangea begin to break into smaller fragments? 180 million years ago in a {} fault the hanging wall block above an inclined fault plane moves downward relative to the other block normal what is a transform fault a strike-slip fault that forms the boundaries between tectonic plates Which of the following best describes a graben? a hanging wall block that has moved down Which one of the following situations results in folding of flat-lying, sedimentary strata? horizontally directed, compressive stresses What type of faults are the products of horizontally directed, extensional stresses? normal faults Which of the following results from thrust faulting? earth's crust is shortened and thickened What types of movement are characteristic in normal and reverse faults? dip-slip How did the mountains and valleys of the Basin and Range Province of the western United States form?

they formed from tensional stresses and normal fault movements In what type of fault does the hanging wall block move up with respect to the footwall block? reverse Which of the following best describes the Great Rift Valley of East Africa? mainly normal faulting as east africa begins to fragment what happens in a reverse fault? The hanging wall block has moved up relative to the footwall block along an inclined fault. which of the following best describes a thrust fault? low angle, reverse fault what happens in a normal fault? The hanging wall block above an inclined fault plane moves downward relative to the lower footwall block. What feature in distorted layered sedimentary rocks are evidence for horizontal compression and shortening? tight folds Which one of the following is consistent with deformation by folding? Horizontal distance is shortened perpendicular to the axes of the folds Which one of the following is consistent with deformation by folding? Horizontal distance is shortened perpendicular to the axes of the folds. Which one of the following statements regarding rock deformation and strength is correct? rupture and plastic deformation occur when stresses exceed the elastic limit Which of the following responses best defines the movement of ice within a glacier? glacial movement is always in a downslope direction Which of the following responses best defines the movement of ice within a glacier?

accumulation of snow is greater than wastage Which of the following best describes the position and/or migration of the snowline on an active glacier? the snowline moves downslope when the glacier is advancing Working in a mountain valley that contains an alpine glacier, you discover a series of end moraines in the valley. As you move up toward the glacier, what conclusions can you expect to make about the moraines? the moraines get younger as you get closer to the glacier During the Cold War, a B-52 bomber accidentally dropped an unarmed nuclear device on the Greenland Ice Sheet. Upon returning to the drop zone many years later, the device had gone missing. As a glaciologist on the project, where should you look for the missing device? to find it you should go downslope from the drop zone, in the direction of ice flow where do glaciers form? n places where more snow falls in the winter than melts away in the summer Snowline the elevation above which snow persists throughout the year zone of wastage the part of the glacier where snow melting exceeds snow accumulation Under what conditions will the front of a glacier remain stationary?

when melting and snow accumulation are equal end moraine ridge of debris deposited at the end of a glacier how does an end moraine form? Pieces of rock are transported to the front of a glacier as ice within the glacier moves will plucking occur even if a glacier is not advancing? Yes, because glacial ice is still moving inside the glacier even if the glacier's front is not advancing. A __________ is defined as a chain of glacial lakes where each lake flows into the next. pater noster lake forms between two u shaped glacial valleys horn peak where the sides have been eroded by glaciers What is the name for an isolated boulder of unexpected rock type that has been transported by a glacier and stranded after the ice melts? erratic what causes a crevasse to form? When ice flows around a bend or over an obstacle, it is stretched and torn, causing large cracks to form. What causes streams that emerge from glaciers to be milk-colored? the presence of finely ground sediment called rock flour most modern glaciers are... Which two regions currently contain the world’s last remaining ice sheets?

anartica and greenland When was the last time North America had major ice sheets 18,000 years ago Which landform marks the furthest extent of an advancing glacier? terminal moraine What feature is responsible for creating eskers? streams Which orbital effect describes how the shape of Earth’s orbit around the Sun will change over tim eccentricity What is the critical latitude for incoming solar radiation, which could affect the formation of ice sheets? 65 N How many years does one complete cycle of precession take? 26,000 years What effect will an increased angle of tilt have on the Earth’s climate? warmer summers and cooler winters Which of the following scenarios will have the greatest chance of triggering an ice age? eccentricity....least amount of solar radiation A(n) ________ would logically be situated next to a large end moraine or terminal moraine. outwashed plain What type of moraine is formed by the merging of two lateral moraines at a junction of two valley glaciers? medial the shore is affected by a complex interaction between...

sea level and local geology How many people want to live in coastal areas 80% the line that marks the contact between land and sea shore extends between the lowest tide level and the highest elevation affected by waves coast extends inland from the shore as far as ocean related features are found coastline marks the coast's seaward edge foreshore area is exposed at lowtide and submerged at high tide backshore area is found landward of high tide mark near shore lies between the low tide shoreline and the point where the waves break at low tide offshore zone is seaward of the near shore zone beach accumulation of sediment found along the landward margin of an ocean or lake beaches are composed of one or more berms relatively flat platform composed of sand beach face wet sloping surface that extends from the berm to shoreline waves are the visible evidence of...

energy passing through a medium {} waves provide most of the enrgy that shapes or modifies shore lines wind-generated most waves derive their energy and motion from {} the wind the distance that the wind has traveled accross open water as the wave gets highter it becomes tooo steep and eventually {} breaks turbulent water created by breaking waves abrasion grinding action of water with rock fragments - erosional force of waves which season has light waves which cause the berm to widen? summer which season has powerful storm waves which erode the berm? winter wave refraction causes waves to... arrive nearly parallel to the shore sediment is transported along the beach force in a zig zag pattern called {} beach drift flow in opposite direction of breaking waves wave cut platforms a sea arch forms when... two sea caves meet a sea stack forms when...

the arch of a sea arch falls spit elongated ridge of sand extending from the land into the mouth of an adjacent bay baymouth bar spit that expands across a bay to seal it off from the ocean tombolo a ridge of sand that connects an island to the mainland or another island barrier islands low ridges of sand that parallelto the coast 3 to 30 km offshore hard stabilization structures built to protect the coast from erosion groins built perpindicular to the beach adn extend into the ocean {} is built offshore and {} is built onshore breakwater; sea wall adding large quantities of sand to the beach when do hurricanes form late summer and early fall greatest wind speed adn heaviest rain of a hurricane occurat the{} eye wall large dome of water that sweeps accross the coast when a hurricane makes landfall {} is the most obvious type of hurricane but not the most deadly wind damage daily changes in the elevation of the ocean surface spring tides produce especially high and low tides neap tides produce a small tidal range a diurnal tidal pattern is characterized by...

a single high tide and a single low tide each day semidiurnal tidal pattern two high tides and two low tides each day mixed tidal pattern two high and low each day, but theyre unequal flood currents tidal deltas created by tidal currents If the wavelength of a set of waves is 20 feet long, how deep is the wave base? 10 ft below the surface How shallow must the ocean floor be for waves to start to break for a wave set with a wavelength of 20 feet? waves will break when the ocean floor is 10 feet below A set of waves are moving from east to west. Assuming the boat is in deep water, which of the following would describe the motion of a boat during the passage of these waves? the boat would move up and down waves hitting at an angle and then bending around features of the coast is known as {} wave refraction landforms assoiciated with longshore drift from where the {} is ample sediment the direction of sand transport {} to the coast parallel the direction of waves approaching the coast must not be {} ini order to produce longshore drift perpendicular What is the name of the gigantic boulders left behind as the glaciers receded?

erratics A thin peninsula called a spit extends beyond the bluffs of the outer beach on Cape Cod. What has caused this spit to form? sand from the bluffs is carried and deposited by long shore currents If the sediment that makes up the beaches of Cape Cod were to lithify, what kind of rock would it become? sand stone What do we call the tide that occurs when constructive interference between lunar and solar bulges produces a large tidal range? Spring Tide Why are high tides found simultaneously on opposite sides of Earth? The tidal bulges occur on both sides of Earth that are aligned with the tide-generating body What is an interference pattern? the wave pattern produced when two or more waves interact What results when two waves, in phase and with the same wavelength, interact? a wave with an amplitude that is the sum of the amplitudes what does the term "in phase" refer to? Waves in phase have identical wavelengths and are aligned peak-to-peak and trough-to-trough When will perfect constructive interference occur for waves that are in phase and moving at the same velocity? when waves with identical wave lengths interfere When will perfect destructive interference occur?

when two waves that are 180 degrees out of phase interfere A ridge of sand projecting into a bay and often having a hooked end is a ________. spit what currents move sand and water parallel to the beach? longshore Which tides are the maximum-amplitude tides produced when the Sun, Earth, and Moon are aligned? spring tides What is the name of a natural sandbar or low sand ridge that connects one island to another island or to the mainland? tombolo What is the name of a natural sandbar or low sand ridge that connects one island to another island or to the mainland? tombolo what is a deep water wave? A wave where the water depth exceeds one-half the wavelength Which of the following is true regarding the gravitational forces affecting Earth? the lunar force is about twice that of the sun Which of the following tides is an incoming or rising tide? flood What type of hard stabilization structure is built more or less parallel to the beach? seawall Which of the following describes a baymouth bar? a sandbar extending across a former inlet to a bay or estuary Which of the following pairs of words refer to the movements of sand and water on a beach due to a breaking wave?

backwash and swash Which one of the following would prove that a coastline is emergent? elevated wave cut terraces What feature erodes and leads to enlargement and extension of a wave-cut platform in the inland direction? wave cut cliff Chapter 10 - Deformation, Mountain Building, and Earth's Crust at University of Wisconsin - Oshkosh - StudyBlue Shear Compression Stress & Where it Occurs rocks or any other object are squeezed or compressed by forces directed toward one another along the same line. Rock layers tend to be shortened in the direction of stress by folding or fracturing. Occurs along convergent plate boundaries, where plates are colliding into one another. Tension Stress & Where it Occurs results from forces acting along the same line, but in opposite directions. Rock layers tend to be lengthened and faulted. Occurs along divergent plate boundaries, where plates are pulling away from each other. Shear Stress & Where it Occurs forces act parallel to one another in opposite directions. Rock layers tend to be displaced along closely spaced planes. Occurs along tranform plate boundaries, where plates are sliding past one another. Strain The deformation that results from stress. The type of strain depends on the type of material (brittle vs.

ductile), the rate of stress being applied (rapidly – more likely to fracture), and location (deeper = higher temperature and pressure). Three Types of Strain the maximum angle and direction of an inclination of a surface. It is measured with a compass at right angles to the direction of the strike. How are Strikes & Dips shown on Geological Maps? Strikes are indicated on geologic maps by a long line oriented in the compass direction of the strike. Dips are indicated on geologic maps by a short line perpendicular to the strike line. Next to the symbols, the angle measurement of the dip is given. Fold A type of geologic structure where rock layers have been permanently bent by plastic strain. There are two main types of folds - anticlines & synclines. Two Main Types of Folds Anticline Syncline Anticline Fold an up-arched fold in rock layers that resembles an arch ∩. The oldest rock layers are in the center at ground surface. All layers dip away from axis. Syncline Fold a down-arched fold in rock layers that resembles a smiley face or a U. The youngest rock layers are in the center. All layers dip toward axis.

Anticline/Syncline Fold Axial Planes These folds have an axial plane that connects the maximum curvature points of each layer, separating the anticline from a syncline. This plane divides the folds in half, with each half being called a limb. Because folds are often found in alternating anticlines and synclines, the anticline and syncline next to one another share a limb. Fault Plane the flat surface along where the break or shear of a fault occurs. Hanging Wall Block consists of the rocks hanging above the fault. In a normal fault, the hanging wall block moves down relative to the footwall block. Footwall Block consists of the rocks beneath the fault. Dip-Slip Faults The blocks on opposite sides of the fault move parallel to the direction of dip, meaning they move up or down along the fault plane. Three Types of Dip-Slip Faults Normal Fault Thrust Fault Normal Fault The hanging wall block slides down relative to the footwall block. The footwall block slides up relative to the hanging wall block. They result from tension where crust is being stretched and thinned. Reverse Fault The hanging wall block slides up relative to the footwall block and the footwall block slides down relative to the hanging wall block.

Formed from compression at convergent plate boundaries where mountains are formed. Thrust Fault The hanging wall block slides up relative to the footwall block (like in a reverse fault) but the fault has a dip of less than 45 degrees. Formed from compression at convergent plate boundaries where mountains are formed. Strike-Slip Fault & Types of Strike-Slip Faults The blocks on opposite sides of the fault move past one another horizontally. They result from shear stress. They are either right-lateral or left-lateral, depending on which way the opposite block appears to have moved. The San Andreas Fault is a right-lateral strike-slip fault. Transform faults are a type of strike-slip fault where two tectonic plates slide past one another. Continental Accretion The processes in which continents grow by orogenies, where additions of Earth materials are added along their margins. Most of the material added to continental margins is eroded older continental crust. Principle of Isostasy The phenomenon of Earth’s crust floating in the denser mantle. Where the crust is the thickest (beneath mountains) it sinks farther down into the mantle and at the same time rises higher above the surface to maintain equilibrium below and above the surface.

This is strange because both crust and mantle are solids, but mantle is very hot and behaves like a viscous fluid under tremendous pressure. Since continental crust stands higher than oceanic crust. Isostatic Rebound The phenomenon where the crust gets loaded (glacial ice weighing down the surface) and lowers down in the upper mantle, but eventually the crust unloads itself (when vast glaciers melt or deep erosion occurs) which causes it to rise back up until it attains equilibrium with the underlying upper mantle. Mountain Any area of land that stands significantly higher (at least 300 m) from the surrounding country and has a restricted summit area. Mountain Range Numerous mountains that are arranged in a linear fashion and are related in age and origin. Mountain System

Question: What is the term for a fold of the Earth's crust in which the layers of rock dip inwards?
Answer: Syncline